A lot of digital design can be done at the abstract level of Boolean algebra with complete disregard for the physical details of the digital devices that will ultimately implement the design. However, there are a number of important physical characteristics of digital devices that need to be understood in order to successfully design circuits since they can and do affect the performance of the circuits. For example, the time it takes a gate to change from L to H or vice versa determines the speed of the device and hence of the circuit.
ANU Engineering - ENGN2211